Vacuum-responsive voltage generator for a fuel injection system

ABSTRACT

An arrangement for generating an irregularly varying voltage for an automobile fuel injection system includes a potentiometer having a plurality of voltage input taps connected to taps on a voltage divider, and an output tap movable along the potentiometer by a vacuum motor which responds to the pressure in the intake manifold of the automobile engine. The voltage input taps are elongated and are adjustable longitudinally and angularly to provide the required voltage distribution on the potentiometer.

United States Patent Inventor Richard B. Beishir St. Louis, Mo.

Appl. No. 11,428

Filed Feb. 16, 1970 Patented Oct. 12, 1971 Assignee ACF Industries,Incorporated New York, N.\.

VAC UUM-RESPONSIVE VOLTAGE GENERATOR FOR A FUEL INJECTION SYSTEM 5Claims, 4 Drawing Figs.

11.5. CI 123/32 EA, 123/119 R, 338/120, 338/176 Int. Cl F02n 5/12, F02m39/00 Field of Search 73/119;

338/120,160,162,176,l79,180185,l88,137, 117, 118; 123/32 EA ReferencesCited UNITED STATES PATENTS 6/1955 Goeppinger et al. 3/1957 Matthew 18/1966 Anderson 3/1970 Long Primary Examiner-Mark M. Newman AssistantExaminer-Cort R. Flint Attorney-Edward H. Casey ABSTRACT: An arrangementfor generating an irregularly varying voltage for an automobile fuelinjection system includes a potentiometer having a plurality of voltageinput taps connected to taps on a voltage divider, and an output tapmovable along the potentiometer by a vacuum motor which responds to thepressure in the intake manifold of the automobile engine. The voltageinput taps are elongated and are adjustable longitudinally and angularlyto provide the required voltage distribution on the potentiometer.

PATENTEBUBHZIHY: 3.612.008

SHEET 1 0F 2 2 TO INTAKE MANIFOLD FUEL DELIVERY.

VACUUM -|N. HG.

INVENTOR RICHARD E5. 'BEISHIR ATTORNEY.

PATENTED 0m 1 2 IB'ZI SHEEI 2 [1F 2 E F TO g/ACUUM T T M TOR. I I

)T f Y 2 Z 2 $1 4 ELECTRONIC \28 TIME - CONTROL.

E? F/F- CONTROL VOLTAGE// GENERATOR.

FIG. 4.

INVENTOR RICHARD E5 BIESHIR ATTORNEY.

VACUUM-RESPONSIVE VOLTAGE GENERATOR FOR A FUEL INJECTION SYSTEMBACKGROUND OF THE INVENTION In electronically controlled fuel injectionsystems it is important to control the rate of fuel feed, and hence theairfuel ratio, precisely according to a predetermined optimum schedule,in order to keep exhaust emissions to a minimum. A principal engineparameter is the intake manifold pressure drop, since it is a measure ofthe airflow per cycle. The manifold pressure drop varies with enginespeed and throttle valve position. The optimum fuel schedule, for atleast some engines, requires a voltage versus manifold pressure dropcurve having varying curvature and several sharp breaks or changes ofcurvature. It is an object of the invention, therefore, to produce anoutput voltage closely in accordance with such a curve over the entireoperating range of the engine.

SUMMARY OF THE INVENTION In an electronically controlled fuel injectionsystem a voltage is produced having a desired variation as a function ofthe intake manifold pressure. A potentiometer has an output tap movableby a piston motor which is connected to sense and respond to themanifold pressure. The potentiometer has a smooth resistive coating on aflat strip and a plurality of voltage input taps. These taps have alinear knife edge resting on the resistive strip and can be turned aswell as moved longitudinally. Each input tap is connected to a separatetap on a voltage divider circuit, so that a different voltage can besupplied to each input tap of the potentiometer. Thus, great flexibilityis obtained in adjusting the output voltage characteristic of thepotentiometer.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a diagram of an arrangementaccording to the invention.

FIG. 2 is a section taken along line 2-2 of FIG. 1.

FIG. 3 is a circuit diagram of the apparatus of FIG. 1.

FIG. 4 is a diagram of a fuel injection system utilizing the apparatusof the invention.

FIG. 5 is a plot of fuel delivery versus manifold vacuum for a fuelsystem employing the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT One type of fuel injectionsystem in which the present invention may be used is shown in FIG. 4.Control voltage generator 10, according to the invention, includes avacuum sensor (described below) connected by pipe 12 to intake manifold14 of an internal combustion engine at a point below throttle valve 16.Voltage generator has output terminals E, F connected to electroniccontrol circuits 18 designed to generate pulses having a durationdetermined by the value of the voltage produced by generator 10. Controlcircuits 18 are triggered by pulses produced by switch 20, which isactuated by cam 22 driven by the engine, so that switch applies a pulsefrom battery 24 to control circuits 18 during each switch closing. Theoutput pulses of circuits 18 are fed through a suitable amplifier 26 tothe solenoids 28 of a plurality of solenoid injection valves, whichremain open for the duration of the pulses supplied to them, and therebycontrol the amount of fuel fed to the engine. Systems of this type arewell known in the art.

In order to obtain maximum engine power and minimum exhaust emissionsthroughout the engine operating range, the fuel supply must be variedprecisely in a complex manner in response to the manifold vacuum. Toachieve this result, voltage generator 10 is required to have apredetermined voltage characteristic having three sharply distinctsections of varying curvature, including a section of small slope,another section of medium slope, and a section having a large slope. Theapparatus 10 shown in FIGS. 1 to 3 for obtaining the required voltagecharacteristics includes a voltage source connected to terminal 30,variable resistors 32, 34, voltage divider 36, and ground terminal F.The voltage divider 36 has a number of parallel connected potentiometers38 to 43, and end terminals 44, 46. Potentiometer 50 has end terminals52, 54 connected to terminals 44, 46. The movable taps of potentiometers38 to 43 are connected to movable taps 56-61 of potentiometer 50. Taps56-61 are slidable in slot 62 of support plate 64, and are turnable todifferent angles. Each tap has an elongated edge 66 in contact with thesmooth flat surface of resistor strip 67 of potentiometer 50. Resistorstrip 67 may include a strip of insulation having a long-wearingresistive coating. The uppermost end of each tap is threaded to receivea locknut 68 for holding its tap in position.

Output tap 70 is slidable in slot 72 of plate 64. Tap 70 is connected tooutput terminal E by wire 74, and is moved by vacuum motor 76. Thelatter includes piston 78 movable. in housing or cylinder 80. Coilspring 82 urgespiston 78 tothe left. Conduit 12 applies the vacuum ofpressure drop in the in- 1 take manifold to the right-hand end ofcylinder 80. Thus, the

higher the vacuum the more piston 78 is moved by air pressure to theright, against the action of spring 82, causing a similar the values ofresistances 38-43 are known, the variable resistors can be replaced withfixed resistors and the system will then operate satisfactorily for theparticular engine-vehicle combination. Variable resistors 32, 34 areretained as shown and are used for making slight adjustments in fueldelivery for curb idle and wide open throttle conditions.

The knife edges 66 are useful primarily as a calibration expedient. Oncethe location and orientation of these edges are determined for aparticular engine-vehicle combination, they can be replaced, if desired,by some form of easily manufactured electronic circuitry. An example ofsuch permanent taps would be the familiar printed circuit or even simplesolder bars or strips laid down on the surface of the conductive plastic67.

From the foregoing, it is apparent that the rather complex device ofFIG. I can be reduced to a simple, low cost electrical circuit usingfixed resistors and conventional techniques to replace the manyvariables shown. This of course would be done after the system is fullycalibrated for a given engine.

Referring to FIG. 5, fuel delivery is plotted against manifold vacuumfor a typical engine. Since the injection system delivers apredetermined quantity of fuel for each stroke of each cylinder, thefuel delivery as plotted can be considered to be the amount of fueldelivered for two full revolutions of the engine, e.g. one power strokefrom each cylinder. Fuel delivery curve has a portion A of little sloperepresenting curb idle and low part throttle operating conditions of theengine. The portion 8" represents heavier part throttle load and theportion C is representative of maximum load and/or wide open throttle.

To calibrate a fuel injection system for a given engine so as tominimize exhaust emissions, the apparatus shown in FIG. 1 can beadjusted to the degree necessary to cause the fuel delivery curve tohave an optimum form, for example, as shown in FIG. 5. Of course forother engines the curve may shift in some degree or other. The necessarycalibrating adjustments are achieved by sliding contact arrangements 56through 61 to any necessary position to match the desired fuel deliverycurve. At the same time each blade 66 can be rotated if necessary tofurther refine the matching characteristics of the curve. Finally any orall of the potentiometers 38 through 43 can be adjusted and when this isaccomplished the fuel delivery curve should be exactly as desired. Oncethe values for the resistances 38-43 are known then each can be replacedwith suitable fixed resistances for economical and low cost manufactureof a complete system for a given engine vehicle combination.

lclaim:

1. In a fuel injection system for an automobile internal combustionengine including a potentiometer controlling the rate of fuel injection;means for applying voltage to the potentiometer, the potentiometerhaving a movable output tap, and vacuum sensing means connected to theintake manifold of the engine for moving the output tap in accordancewith the pressure in the intake manifold; electronic control circuitmeans having its input'connected to the movable tap of the potentiometerand its output connected to a plurality of electronically operated fuelinjection valves; the improvement consisting in that the potentiometerincludes an elongated resistive member having a series of input tapsspaced longitudinally therealong; means for mounting each input tap forlongitudinal adjustment and independent transverse adjustment toward andaway from the path of the output tap, said means for applying voltagebeing connected to each input tap for applying independently adjustablevoltages thereto.

2. Apparatus according to claim 1 wherein said input taps have anelongated substantially linear contact with said resistive member andeach of said input taps is adjusted transversely by rotating the line ofcontact of each tap on the resistive member.

3. In a fuel injection system for an automobile internal combustionengine including a potentiometer controlling the rate of fuel injection;means for applying voltage to the potentiometer, the potentiometerhaving a movable output tap, and

vacuum sensing means connected to the intake manifold of the engine formoving the output tap in accordance with the pressure in the intakemanifold; electronic control circuit means having its input connected tothe movable tap of the potentiometer and its output connected to aplurality of electronically operated fuel injection valves; theimprovement consisting in that the potentiometer includes an elongatedflat resistive strip having resistive material on at least one surfacethereof; a row of input taps on one side of the resistive strip spacedlongitudinally therealong, the path of the movable tap being parallel toand near one edge of said resistive strip, said means for applyingvoltage being connected to the input taps for applying progressivelyincreasing adjustable voltages thereto, each of said input taps havingan elongated narrow edge in contact with said surface of the resistivestrip; and means for mounting said input taps for limited longitudinaladjustment along the resistive strip and for rotation of the elongatededge of each input tap on the resistive strip.

4. Apparatus according to claim 3, wherein each input tap is turnablefor setting the line of contact thereof with the resistive strip to anyangle between a longitudinal and a transverse position.

5. Apparatus according to claim 4, wherein the input taps have aninverted T-shape consisting of a stem perpendicular to the surface ofthe resistive strip and a blade at the end of the stem having anelongated edge in contact with the surface of the resistive strip, saidstem being rotatable on its axis for turning the elongated edge thereof.

1. In a fuel injection system for an automobile internal combustionengine including a potentiometer controlling the rate of fuel injection;means for applying voltage to the potentiometer, the potentiometerhaving a movable output tap, and vacuum sensing means connected to theintake manifold of the engine for moving the output tap in accordancewith the pressure in the intake manifold; electronic control circuitmeans having its input connected to the movable tap of the potentiometerand its output connected to a plurality of electronically operated fuelinjection valves; the improvement consisting in that the potentiometerincludes an elongated resistive member having a series of input tapsspaced longitudinally therealong; means for mounting each input tap forlongitudinal adjustment and independent transverse adjustment toward andaway from the path of the output tap, said means for applying voltagebeing connected to each input tap for applying independently adjustablevoltages thereto.
 2. Apparatus according to claim 1 wherein said inputtaps have an elongated substantially linear contact with said resistivemember and each of said input taps is adjusted transversely by rotatingthe line of contact of each tap on the resistive member.
 3. In a fuelinjection system for an automobile internal combustion engine includinga potentiometer controlling the rate of fuel injection; means forapplying voltage to the potentiometer, the potentiometer having amovable output tap, and vacuum sensing means connected to the intakemanifold of the engine for moving the output tap in accordance with thepressure in the intake manifold; electronic control circuit means havingits input connected to the movable tap of the potentiometer and itsoutput connected to a plurality of electronically operated fuelinjection valves; the improvement consisting in that the potentiometerincludes an elongated flat resistive strip having resistive material onat least one surface thereof; a row of input taps on one side of theresistive strip spaced longitudinally therealong, the path of themovable tap being parallel to and near one edge of said resistive strip,said means for applying voltage being connected to the input taps forapplying progressively increasing adjustable voltages thereto, each ofsaid input taps having an elongated narrow edge in contact with saidsurface of the resistive strip; and means for mounting said input tapsfor limited longitudinal adjustment along the resistive strip and forrotation of the elongated edge of each input taP on the resistive strip.4. Apparatus according to claim 3, wherein each input tap is turnablefor setting the line of contact thereof with the resistive strip to anyangle between a longitudinal and a transverse position.
 5. Apparatusaccording to claim 4, wherein the input taps have an inverted T-shapeconsisting of a stem perpendicular to the surface of the resistive stripand a blade at the end of the stem having an elongated edge in contactwith the surface of the resistive strip, said stem being rotatable onits axis for turning the elongated edge thereof.